Method and system for an aspirator for a brake booster

ABSTRACT

Methods and systems are provided for providing vacuum to a brake booster via an aspirator system. In one example, a system may include an aspirator system fluidly coupled with a brake booster with no intervening components located therebetween.

FIELD

The present description relates generally to an aspirator for a brakebooster.

BACKGROUND/SUMMARY

Vehicle control systems may be configured to start an engine assuming agiven intake manifold volume. However, interactions between vacuumlevels in a brake booster and the intake manifold pressure at enginestarts can cause variability in the air charge, and consequentlyair-to-fuel ratio at the engine starts. As such, this increases exhaustemissions.

One approach to address this variability is shown by Kayama et al. inU.S. Pat. No. 6,857,415. Therein, a valve is placed between the brakebooster and the intake manifold to equalize the (remaining) pressure inthe brake booster to atmospheric levels or to remove air from the intakemanifold to the brake booster.

However, the inventors herein have identified a potential issue withsuch an approach. As one example, the valve used in the approach ofKayama et al. does not allow the level of intake manifold pressure (MAP)to be set from one engine start to another engine start. As anotherexample, even with the valve, a consistent MAP level may not be attainedat engine starts occurring at high altitudes as well as at sea level.Further, the valve may be controlled by a control system with electricsignals which may increase an overall cost of production.

In one example, the issues described above may be addressed by anaspirator system comprising a volute shaped aspirator with a linearaspirator protruding through a spiral of the volute aspirator, thelinear aspirator comprising a venturi passage fluidly coupled to a brakebooster, and where the aspirators are fluidly coupled to front or reargrills via a conical aspirator with no other intervening componentslocated therebetween. In this way, vacuum may be provided to the brakebooster without flowing suck flow from the brake booster to an engine orany components of the engine.

As one example, the aspirators receive motive flow through the frontgrill and generate vacuum based on geometries of the linear aspirator,the volute aspirator, and the conical aspirator. The vacuum may beprovided to the brake booster when the check valve is open based on avacuum of the brake booster being less than a minimum threshold vacuum.The vacuum draws suck flow from the brake booster to the aspiratorsystem. The suck flows mixes with the motive flow and flows through theaspirators and out the rear grill without flowing through any othercomponents.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example engine with a single cylinder.

FIG. 2 shows a vehicle comprising the engine and an aspirator systemcoupled to a brake booster.

FIG. 3 shows a shape of first, second, and third aspirator geometries ofthe aspirator system.

FIG. 3 is shown approximately to scale.

FIG. 4 shows a method for providing vacuum to the brake booster.

FIG. 5 shows a chart detailing vacuum level in the brake booster basedon vehicle conditions.

DETAILED DESCRIPTION

The following description relates to an example of an aspirator systemfor providing vacuum to a brake booster. A general schematic of anengine is shown in FIG. 1. A vehicle with the engine and the aspiratorcoupled to the brake booster is shown in FIG. 2. First, second, andthird aspirator portions are shown in detail in FIG. 3. The portions areall in fluid communication. The first portion is fluidly coupled to thebrake booster when a check valve is in an open position. The aspiratorsystem may draw suck flow from the brake booster while providing vacuumto the brake booster. The suck flow may mix with motive flow in theaspirator system and flow out the aspirator system without flowing toany intervening components therebetween. A method for providing vacuumto the brake booster is shown in FIG. 4. A chart showing brake boostervacuum level changes based on vehicle operations is shown in FIG. 5.

FIG. 3 shows example configurations with relative positioning of thevarious components. If shown directly contacting each other, or directlycoupled, then such elements may be referred to as directly contacting ordirectly coupled, respectively, at least in one example. Similarly,elements shown contiguous or adjacent to one another may be contiguousor adjacent to each other, respectively, at least in one example. As anexample, components laying in face-sharing contact with each other maybe referred to as in face-sharing contact. As another example, elementspositioned apart from each other with only a space there-between and noother components may be referred to as such, in at least one example.

Continuing to FIG. 1, a schematic diagram showing one cylinder of amulti-cylinder engine 10 in an engine system 100, which may be includedin a propulsion system of an automobile, is shown. The engine 10 may becontrolled at least partially by a control system including a controller12 and by input from a vehicle operator 132 via an input device 130. Inthis example, the input device 130 includes an accelerator pedal and apedal position sensor 134 for generating a proportional pedal positionsignal. A combustion chamber 30 of the engine 10 may include a cylinderformed by cylinder walls 32 with a piston 36 positioned therein. Thepiston 36 may be coupled to a crankshaft 40 so that reciprocating motionof the piston is translated into rotational motion of the crankshaft.The crankshaft 40 may be coupled to at least one drive wheel of avehicle via an intermediate transmission system. Further, a startermotor may be coupled to the crankshaft 40 via a flywheel to enable astarting operation of the engine 10.

The combustion chamber 30 may receive intake air from an intake manifold44 via an intake passage 42 and may exhaust combustion gases via anexhaust passage 48. The intake manifold 44 and the exhaust passage 48can selectively communicate with the combustion chamber 30 viarespective intake valve 52 and exhaust valve 54. In some examples, thecombustion chamber 30 may include two or more intake valves and/or twoor more exhaust valves.

In this example, the intake valve 52 and exhaust valve 54 may becontrolled by cam actuation via respective cam actuation systems 51 and53. The cam actuation systems 51 and 53 may each include one or morecams and may utilize one or more of cam profile switching (CPS),variable cam timing (VCT), variable valve timing (VVT), and/or variablevalve lift (VVL) systems that may be operated by the controller 12 tovary valve operation. The position of the intake valve 52 and exhaustvalve 54 may be determined by position sensors 55 and 57, respectively.In alternative examples, the intake valve 52 and/or exhaust valve 54 maybe controlled by electric valve actuation. For example, the cylinder 30may alternatively include an intake valve controlled via electric valveactuation and an exhaust valve controlled via cam actuation includingCPS and/or VCT systems.

A fuel injector 69 is shown coupled directly to combustion chamber 30for injecting fuel directly therein in proportion to the pulse width ofa signal received from the controller 12. In this manner, the fuelinjector 69 provides what is known as direct injection of fuel into thecombustion chamber 30. The fuel injector may be mounted in the side ofthe combustion chamber or in the top of the combustion chamber, forexample. Fuel may be delivered to the fuel injector 69 by a fuel system(not shown) including a fuel tank, a fuel pump, and a fuel rail. In someexamples, the combustion chamber 30 may alternatively or additionallyinclude a fuel injector arranged in the intake manifold 44 in aconfiguration that provides what is known as port injection of fuel intothe intake port upstream of the combustion chamber 30.

Spark is provided to combustion chamber 30 via spark plug 66. Theignition system may further comprise an ignition coil (not shown) forincreasing voltage supplied to spark plug 66. In other examples, such asa diesel, spark plug 66 may be omitted.

The intake passage 42 may include a throttle 62 having a throttle plate64. In this particular example, the position of throttle plate 64 may bevaried by the controller 12 via a signal provided to an electric motoror actuator included with the throttle 62, a configuration that iscommonly referred to as electronic throttle control (ETC). In thismanner, the throttle 62 may be operated to vary the intake air providedto the combustion chamber 30 among other engine cylinders. The positionof the throttle plate 64 may be provided to the controller 12 by athrottle position signal. The intake passage 42 may include a mass airflow sensor 120 and a manifold air pressure sensor 122 for sensing anamount of air entering engine 10.

An exhaust gas sensor 126 is shown coupled to the exhaust passage 48upstream of an emission control device 68 according to a direction ofexhaust flow. The sensor 126 may be any suitable sensor for providing anindication of exhaust gas air-fuel ratio such as a linear oxygen sensoror UEGO (universal or wide-range exhaust gas oxygen), a two-state oxygensensor or EGO, a HEGO (heated EGO), a NO_(x), HC, or CO sensor. In oneexample, upstream exhaust gas sensor 126 is a UEGO configured to provideoutput, such as a voltage signal, that is proportional to the amount ofoxygen present in the exhaust. Controller 12 converts oxygen sensoroutput into exhaust gas air-fuel ratio via an oxygen sensor transferfunction.

The emission control device 68 is shown arranged along the exhaustpassage 48 downstream of the exhaust gas sensor 126. The device 68 maybe a three way catalyst (TWC), NO_(x) trap, selective catalyticreductant (SCR), various other emission control devices, or combinationsthereof. In some examples, during operation of the engine 10, theemission control device 68 may be periodically reset by operating atleast one cylinder of the engine within a particular air-fuel ratio.

An exhaust gas recirculation (EGR) system 140 may route a desiredportion of exhaust gas from the exhaust passage 48 to the intakemanifold 44 via an EGR passage 152. The amount of EGR provided to theintake manifold 44 may be varied by the controller 12 via an EGR valve144. Under some conditions, the EGR system 140 may be used to regulatethe temperature of the air-fuel mixture within the combustion chamber,thus providing a method of controlling the timing of ignition duringsome combustion modes.

The controller 12 is shown in FIG. 1 as a microcomputer, including amicroprocessor unit 102, input/output ports 104, an electronic storagemedium for executable programs and calibration values shown as read onlymemory chip 106 (e.g., non-transitory memory) in this particularexample, random access memory 108, keep alive memory 110, and a databus. The controller 12 may receive various signals from sensors coupledto the engine 10, in addition to those signals previously discussed,including measurement of inducted mass air flow (MAF) from the mass airflow sensor 120; engine coolant temperature (ECT) from a temperaturesensor 112 coupled to a cooling sleeve 114; an engine position signalfrom a Hall effect sensor 118 (or other type) sensing a position ofcrankshaft 40; throttle position from a throttle position sensor 65; andmanifold absolute pressure (MAP) signal from the sensor 122. An enginespeed signal may be generated by the controller 12 from crankshaftposition sensor 118. Manifold pressure signal also provides anindication of vacuum, or pressure, in the intake manifold 44. Note thatvarious combinations of the above sensors may be used, such as a MAFsensor without a MAP sensor, or vice versa. During engine operation,engine torque may be inferred from the output of MAP sensor 122 andengine speed. Further, this sensor, along with the detected enginespeed, may be a basis for estimating charge (including air) inductedinto the cylinder. In one example, the crankshaft position sensor 118,which is also used as an engine speed sensor, may produce apredetermined number of equally spaced pulses every revolution of thecrankshaft.

The storage medium read-only memory 106 can be programmed with computerreadable data representing non-transitory instructions executable by theprocessor 102 for performing the methods described below as well asother variants that are anticipated but not specifically listed.

The controller 12 receives signals from the various sensors of FIG. 1and employs the various actuators of FIG. 1 to adjust engine operationbased on the received signals and instructions stored on a memory of thecontroller.

FIG. 2 shows a vehicle 200 comprising an engine 208 with a cooling fan206. The engine 208 may be used similarly to engine 10 of FIG. 1. Thevehicle 200 further comprises a front end 202 and a back end 204. Theengine 208 and the cooling fan 206 are proximal to the front end 202.The vehicle 200 further comprises a front grill 262 and a rear grill 264which may admit motive flow and expel motive flow from the vehicle,respectively.

The cooling fan 206 may be activated in response to a coolanttemperature exceeding a threshold temperature. The temperature thresholdmay be based on a temperature where the coolant may no longersufficiently cool an engine and or one or more engine components.Coolant temperatures may rise during low vehicle speeds and/or idle whenmotive air through a radiator of the engine 208 is unable tosufficiently cool an engine coolant. In response to the insufficientmotive air, the cooling fan 206 may be activated to decrease atemperature of the engine and/or its components. In this way, thecooling fan 206 may be activated during low vehicle speeds. It will beappreciated by someone skilled in the art that the fan 206 may also beactivated during higher vehicle speeds in order to cool the engine 208and/or one or more of its components.

A brake booster 210 is shown coupled to a brake pedal 212. The brakebooster 210 may include an internal vacuum reservoir to amplify forceprovided by a foot 214 to the brake pedal 212. Vacuum is consumed whenthe pedal 212 is depressed resulting in a pressure increase (or loss ofvacuum) of the brake booster. A vacuum line 216 with a check valve 218couples the brake booster 210 to an aspirator system 220. The aspiratorsystem 220 may provide vacuum to replenish the vacuum of the brakebooster when the check valve 218 is open. The check valve opens when thevacuum of the brake booster 210 decreases below a minimum thresholdvacuum. The minimum threshold vacuum may be based on a vacuum of a firstvacuum portion 230 (e.g., 40000 Pa).

The aspirator system 220 generates vacuum via motive flow from the frontgrill 262 flowing through a first inlet 222 and a second inlet 224.Motive flow provided to the first 222 and second 224 inlets may befluidly separate from the motive flow provided to the engine 208. Thesecond inlet 224 is in fluid communication with a first aspiratorportion 230, indicated by small dashed lines, located proximal to thefront end 202. The first aspirator portion 230 may be a venturi passagewith the vacuum line 216 being coupled to a narrowest portion of theventuri passage. The check valve 218 may remain in a closed position ifthe vacuum of the brake booster is greater than the minimum vacuumthreshold to prevent fluid communication between the booster 210 andfirst aspirator portion 230. For example, the valve 218 may openfollowing the brake pedal being depressed and the vacuum reservoirvacuum level decreasing below the minimum threshold vacuum.

When the check valve 218 is open and the first portion 230 providesvacuum to the brake booster 210, suck flow from the brake booster flowsinto the first portion and mixes with motive flow. The mixture may thenflow through the aspirator system 220 before flowing through the reargrills 264, without flowing to the engine or any engine components.

A second aspirator portion 240, indicated by medium dashed lines, and athird aspirator portion 250, indicated by large dashed lines, arefurther included in the aspirator system. Large dashed lines are biggerthan medium dashed lines which are bigger than small dashed lines. Thesecond aspirator portion 240 may be a volute shape (similar to aturbine) surrounding an outlet of the first aspirator portion 230. Thethird aspirator portion 250 may be a cone shape and expel motive airthrough the rear end 204 into an ambient atmosphere. The secondaspirator portion 240 is proximal to and overlaps a portion of the firstaspirator portion 230. The third aspirator portion 250 is proximal tothe rear end 204 and is fluidly coupled with the rear grill 264.

The aspirator system 220 generates vacuum based on motive air flowingthrough the first 230, second, 240, and third 250 aspirator portions.Motive flow flows through the first inlet 222 and second inlet 224 intothe second portion 240 and the first portion 230, respectively. Themotive flows from the first 230 and second 240 portions combine upstreamof the third portion 250 before being expelled into an ambientatmosphere. Vacuum generated by the third portion may increase vacuumgenerated by the second portion, which may increase vacuum generated bythe first portion. Specifically, the third vacuum geometry 250 maygenerate a vacuum of 5 kPa, the second vacuum geometry 240 may generatea vacuum of 15 kPa, and the first vacuum geometry 230 may generate avacuum of 40 kPa.

During instances of low motive flow, the cooling fan 206 may beactivated to provide motive flow through the first 222 and second 224inlets. In this way, vacuum may be provided by the aspirator system 220to the brake booster 210 during high vehicle speeds, low vehicle speeds,and vehicle stops.

As an example, the vehicle may use stored vacuum within the brakebooster while depressing the brake pedal to slow from a high speed to astop. If the pressure within the brake booster surpasses a thresholdpressure, then the check valve may open, indicating a demand to decreasepressure within the brake booster. As an operator accelerates thevehicle from the stop, the motive air may be insufficient to provide thedesired vacuum to the brake booster. Thus, the cooling fan may beactivated to provide all of or a portion of the motive air through theaspirator system to generate a sufficient vacuum. In this way, thecooling fan may be used to both cool the engine and/or one or moreengine components and provide motive air to the aspirator system. Thecooling fan may be deactivated in response to a vehicle speed generatinga motive flow greater than a threshold flow or to a coolant temperaturedecreasing below the threshold temperature. If the coolant temperaturedecreases below the threshold temperature while the motive flow is lessthan the threshold flow, the cooling fans may be deactivated to preventfurther coolant temperature decrease in a first condition. In a secondcondition, the cooling fans may remain active in response to the coolanttemperature being below the threshold temperature and the motive flowbeing less than the threshold flow to provide vacuum to the brakebooster.

Additionally or alternatively, the aspirator system may provide vacuumto the brake booster simultaneously to the vehicle using vacuum storedwithin the brake booster. The aspirator system continuously receivesmotive flow during vehicle motion and may receive motive flow duringvehicle stops from the cooling fans. Thus, the aspirator system maycontinuously generate vacuum independent of the brake booster desiringvacuum. If the brake booster desires vacuum while the brake pedal isdepressed, then the check valve may open to fluidly connect the brakebooster to the aspirator system. In this way, vacuum of the brakebooster may be replenished while braking with assistance from the brakebooster.

As depicted, the aspirator system 220 and the brake booster 210 are notin fluid communication with the engine 208 and/or any engine componentssuch as those previously presented in FIG. 1 (e.g., intake manifold,compressor, turbine, etc.). In this way, no electrical components areused for the operation of the aspirator system 220 and/or the brakebooster 210. Motive air flows into the aspirator system 220 via thefront end 202 and out the aspirator system 220 via the rear end 204.

FIG. 2 depicts a vehicle with a system comprising an engine with one ormore cooling fans and an aspirator system with at least one inletdownstream of and in fluid communication with the one or more coolingfans. First, second, and third aspirator portions of the aspiratorsystem are fluidly coupled and capable of receiving motive flow from afront grill and expelling the motive flow out through a rear grill. Abrake booster comprising a passage with a check valve is fluidly coupledwith the first aspirator portion with no other intervening componentslocated therebetween. The brake booster may provide vacuum when anoperator depresses a brake pedal of the vehicle. The first aspiratorportion provides vacuum to and receives suck flow from the brake boosterwhen the check valve is open. The suck flow mixes with the motive flowin the first portion and flows toward the third portion and out the reargrill without flowing into the engine.

FIG. 3 shows a system 300 with an aspirator system 302 in fluidcommunication with a vacuum reservoir 342 of a brake booster 340. Asdescribed above, the brake booster 340 may use stored vacuum from thevacuum reservoir 342 to amplify a braking signal from an operatordepressing a brake pedal 348. The aspirator system 302 may replenish thevacuum reservoir 342 in response to the vacuum of the reservoirdecreasing below the minimum threshold vacuum. The aspirator system 302and the brake booster 340 are fluidly connected to an ambient atmosphereand a brake system. The aspirator system 302 and the brake booster 340are not in fluid communication with an engine and or any enginecomponents (e.g., intake manifold, exhaust manifold, compressor,turbine, cylinders, etc). Dashed arrows depict a direction of motiveflow through the aspirator system 302.

The aspirator system 302 comprises three different aspirator generatinggeometries each of which may rely upon flowing motive air from a largerflow path to a smaller flow path. Speed increases and pressure decreases(e.g., vacuum increases) as air flows from the larger path to thesmaller path. The three different geometries may be arranged in seriesand in fluid communication with each other to build vacuum across theaspirator system 302. The aspirator system 302 comprises of threeportions namely, a first aspirator portion 310, a second aspiratorportion 320, and a third aspirator portion 330. The first 310, second320, and third 330 aspirator portions generate vacuum during vehiclespeeds greater than a threshold speed

The third aspirator portion 330 is further downstream (e.g., nearer arear end of a vehicle) than the first 310 and second 320 aspiratorportions. An outlet 332 is located between outer 334 and inner 336 wallsand is in fluid communication with an ambient environment through a reargrills of a vehicle. As an example, motive air flowing through theoutlet 332 flows outside the vehicle and into the atmosphere. A path ofthe outlet 332 may be marginally bigger at an upstream end compared toat the rear end of the vehicle due to geometries of the outer 334 andinner 336 walls. A cross-section of the outlet 334 is substantiallyannular allowing motive air to flow out the rear end in a toroidal(ring) shape. It will be appreciated by someone skilled in the art thatthe outlet 334 may comprise other suitable shapes.

The outer 334 and inner 336 walls are spaced away from each other by awidth of the outlet 332. The outer 334 and inner 336 walls may besubstantially cone-shaped (e.g., conical) with a substantially circularcross-section. The inner wall 336 may be coupled to the outer wall 334via supports (not shown) located between and fixed to the walls. Thewalls are closer to each other near the rear end of the vehicle comparedto near the front end. In other words, the width (e.g., a space) betweenthe outer 334 and inner 336 walls decreases toward the rear of thevehicle compared to near the engine. In this way, motive air flowingthrough the outlet 332 increases in speed and decreases in pressure(e.g., increases vacuum) as it approaches the rear end of the vehicle.In one example, the vacuum produced is equal to 5 kPa. Alternatively,the vacuum produced may be less than or greater than 5 kPa.

The second aspirator portion 320 is located adjacent to and overlaps aportion of the first portion 310. The second portion 320 comprises aninlet 322 located downstream of a first cooling fan 380. As describedabove, the first cooling fan 380 may provide motive air during lowvehicle speeds and/or vehicle stops. A second portion body 324 isfluidly coupled to the inlet 322 and a connecting passage 350 fluidlycoupling the second aspirator portion 320 to the third aspirator portion330. The aspirator body 324 may be a volute (spiral) shape. Motive airfrom the inlet 322 flows in a substantially circular direction around aninterior wall 328 of the second portion body 324 before annularlyflowing into the connecting passage 350.

A second portion outlet 326 is located between the interior wall 328 anda connecting wall 352 of the connecting passage 350. The second portionoutlet 326 is wider near the second portion body 324 compared to nearthe connecting passage 350. The second portion outlet 326 issubstantially ring shaped and directs motive air into the connectingpassage 350 along the connecting wall 352 in a similar ring shape.Motive air may be pulled through the second portion outlet 326 by vacuumgenerated at the third aspirator portion 330. Motive air flowing throughthe second portion outlet 326 decreases in pressure and increases inspeed and creates a vacuum. The vacuum generated by the second aspiratorportion is exactly 15 kPa in one example. Alternatively, the vacuumgenerated by the second aspirator portion may be greater than or lessthan 15 kPa. In this way, the vacuum generated by the second aspiratorportion 320 is more than the vacuum generated by the third aspiratorportion 330.

The first aspirator portion 310 is the furthest upstream (e.g., nearesta front end of a vehicle) of the three portions of the aspirator system302. The first aspirator portion 310 is substantially linear and extendsthrough a spiral of the second aspirator portion 320. The firstaspirator portion comprises an upstream passage 314 and a downstreampassage 316 with a venturi passage 312 located therebetween. Motive flowflows through the venturi passage 312 increasing in speed and decreasingin pressure, resulting in a vacuum. The upstream passage 314 is locateddownstream of a second cooling fan 382, serving as an inlet for thefirst aspirator portion 310. The downstream passage 316 is fluidlycoupled with the connecting passage 350 and extends through an openingof the interior wall 328 (e.g., through the spiral of the second portionbody 324). An extreme end of the downstream passage 316 is interior toan extreme end of the interior wall 328 of the second portion 320. Thesecond aspirator portion 320 may assist a motive air outflow through thedownstream passage 316 and increase a vacuum generated by the firstportion. The downstream passage 316 directs motive air to flow inside ofthe motive air from the second portion outlet 326. In this way, motiveair from the second portion outlet 326 flows between the connecting wall352 and the motive air from the downstream passage 316.

The brake booster 340 is fluidly coupled to the first aspirator portion310 at a narrowest portion of the venturi passage 312 via a vacuum line344. The narrowest portion of the venturi passage 312 may generate amore vacuum than other portions of the venturi passage 312. In oneexample, the vacuum generated at the narrowest portion is 40 kPa.Alternatively, the vacuum generated at the narrowest portion may begreater than or less than 40 kPa. In this way, the first aspiratorportion 310 generates more vacuum than the second 320 and/or third 330aspirator portions.

A check valve 346 is located along the vacuum line 344 and may openbased on the vacuum generated by the first aspirator portion 310. Forexample, the check valve may open when a vacuum of the vacuum reservoir342 is less than a minimum threshold vacuum, which is based on apressure of the first aspirator portion 310. When the valve 346 is open,the first aspirator portion 310 provides vacuum to the vacuum reservoir342 by drawing air from the reservoir 342 into the first aspiratorportion 310.

Generating vacuum in the aspirator system 302 includes flowing motiveair through the venturi passage 312, through the spiral of the secondportion body 324, and through the annular outlet 332.

FIG. 4 shows a method 400 for operating an aspirator system forproviding vacuum to a brake booster. The method 400 may further provideinstructions for operating one or more cooling fans for providing motiveair to the aspirator system during vehicle conditions producinginsufficient motive air. Instructions for carrying out method 400 may beexecuted by a controller (e.g., controller 12 of FIG. 1) based oninstructions stored on a memory of the controller and in conjunctionwith signals received from sensors of the engine system, such as thesensors described above with reference to FIG. 1. The controller mayemploy engine actuators of the engine system to adjust engine operation,according to the methods described below. For example, the controller 12may adjust operation of one or more cooling fans (e.g., cooling fans 380and 382 of FIG. 3) during vehicle operation.

The method 400 may be described in reference to components previouslypresented. Specifically, the method 400 may be described in reference tovehicle 200, brake pedal 212, brake booster 340, aspirator system 302,and check valve 346 of FIGS. 2 and 3.

The method 400 begins at 402 where the method 400 includes determining,estimating, and/or measuring current engine operating parameters. Thecurrent engine operating parameters may include engine speed, coolanttemperature, engine load, vehicle speed, manifold air pressure, manifoldvacuum, and air/fuel ratio.

At 404, the method 400 includes determining if the coolant temperatureis greater than a threshold temperature. The threshold temperature rangemay be based on a desired coolant operating temperature (e.g., 185° F.).Coolant temperatures below the threshold temperature may be too cold andlead to one or more of a catalyst not lighting off, increased condensateformation, and freezing. If the coolant temperature is less than thethreshold temperature, then the method 400 proceeds to 406 to maintaincurrent engine operating parameters and does not activate the coolingfans. The method may proceed to 410, as will be described below.

If the coolant temperature is greater than the threshold temperature,then the method 400 may proceed to 408 to activate the cooling fans toprovide cooling to an engine compartment.

The fans may be variable speed fans such that a flow rate provided bythe fans is controlled by a controller (e.g., controller 12).

At 410, the method 400 includes estimating a brake booster pressure. Thebrake booster pressure may be estimated based on a duration of brakepedal depression and an amount of vacuum replenishment, wherein agreater duration corresponds with a higher brake booster pressure and agreater amount of vacuum replenishment corresponds with a lower brakebooster pressure.

At 412, the method 400 includes determining if vacuum is desired by thebrake booster. Vacuum may be desired if the brake booster pressure isless than a vacuum (e.g., minimum threshold vacuum) of a first aspiratorportion of the aspirator system (e.g., first aspirator portion 310 ofthe aspirator system 302). Additionally or alternatively, vacuum mayalso be desired based on the duration of brake pedal depression andmiles driven. If vacuum is not desired, then the method 400 proceeds to414 to maintain current operating parameters and does not open the checkvalve located between the brake booster and the aspirator system. Motiveair may flow through the aspirator system despite the check valveremaining closed. In this way, motive air is continuously provided tothe aspirator system while the vehicle is in motion.

If vacuum is desired, then the method 400 proceeds to 416 to determineif motive air is less than a threshold flow rate. The threshold flowrate may be based on a motive air flow rate capable of generating vacuumin the aspirator system. The motive air may be below the threshold flowrate for a vehicle speed less than a threshold speed (e.g., vehicledriving at a low speed or at a stop). The motive air may be greater thanthe threshold flow rate for a vehicle driving at mid or high speeds. Ifthe motive air is not less than the threshold flow rate, then the method400 proceeds to 418 to open the check valve and provide vacuum to thebrake booster from the aspirator system. One or more cooling fans arenot activated in order to provide motive flow to the aspirator system.However, it will be appreciated that the cooling fans may be activatedbased on other conditions (e.g., coolant temperature exceeding thethreshold temperature). The check valve is automatically opened by apressure of the brake booster being greater than a pre-loaded pressureof the check valve. As an example, the check valve may be springactuated and a pressure of the spring is overcome when the brake boosterpressure exceeds the threshold pressure (e.g., 40 kPa). The check valveis not opened by an electronic signal.

If the motive air is less than the threshold flow rate, then the method400 proceeds to 420 determine if the cooling fans are off. If thecooling fans are already activated due to other vehicle conditions(e.g., coolant temperature is greater than the threshold temperature),then the method 400 proceeds to 418 as described above.

If the cooling fans are off and the motive flow is less than thethreshold flow rate, then vacuum may not be produced by the aspiratorsystem and the method 400 proceeds to 422 to activate the cooling fans.The controller may signal activation of the cooling fans in response tothe determination of the motive air being less than the threshold flowrate. The cooling fans rotate and provide motive flow to both the firstaspirator portion and a second aspirator portion of the aspiratorsystem.

Additionally or alternatively, the cooling fans may not be activated inresponse to the motive flow being less than the threshold flow rate dueto the coolant temperature being less than the threshold temperature. Inthis way, the fans remain inactive to prevent condensate formationand/or condensate freezing which may degrade engine performance undersome conditions. Under other conditions, the cooling fans may beactivated in response to the motive flow being less than the thresholdflow rate and the coolant temperature being less than the thresholdtemperature to provide vacuum to the brake booster. Engine operation maybe adjusted to prevent condensate formation and/or freezing byincreasing EGR, retarding spark, decreasing an air/fuel ratio,increasing a primary injection pressure, increasing a second injectionvolume, and other suitable adjustments capable of increasing coolanttemperature. Additionally or alternatively, the adjustments may furtherinclude disabling coolant flow. Furthermore, a rotation speed of thecooling fans may be reduced to a minimum speed capable of providing thedesired flow to the aspirator system for producing vacuum. By doingthis, cooling of the coolant is decreased while vacuum is generated bythe aspirator system and provided to the brake booster.

At 424, the method 400 includes opening the check valve and providingvacuum to the brake booster from the aspirator system. The method 400may continue to operate the cooling fans until the motive flow exceedsthe threshold flow rate or until the coolant temperature are less thanthe threshold temperature. Additionally or alternatively, the coolingfans may be continuously operated.

FIG. 5 shows a chart 500 depicting an example brake booster vacuum levelbased on vehicle operations and modifications of vehicle operations.Chart 500 shows brake pedal position at plot 502, brake booster vacuumlevel at plot 504, vehicle speed at plot 506, cooling fan status at plot508, and check valve position at plot 510. All of the above are plottedagainst time on the X-axis. Line 505 represents a minimum thresholdvacuum in the brake booster vacuum reservoir. Line 507 represents athreshold vehicle speed unable to provide sufficient motive flow to theaspirator system to generate vacuum.

Prior to time t1, a vehicle may be moving in a steady state conditionwith moderate speed. Brake pedal is in a released (or “off”) positionand brake booster vacuum is sufficient, as indicated by the brakebooster vacuum 504 being higher than the minimum threshold vacuum 505.The check valve between the brake booster and the aspirator system isclosed due to the sufficient vacuum in the brake booster. The brakebooster and the aspirator system are not in fluid communication when thecheck valve is in the closed position. The cooling fans are notactivated (or “off”) due to sufficient motive flow being delivered tothe aspirator system, as indicated by the vehicle speed 506 being abovethe threshold vehicle speed line 507.

At t1, the brake pedal may be applied by the operator upon which vacuumin the brake booster is consumed to enable wheel braking. Between t1 andt2, as the brake application continues, the brake booster vacuumdecreases (e.g., a pressure in the brake booster vacuum reservoirincreases). However, the level of vacuum within the reservoir remainsabove the minimum threshold vacuum 505 and the check valve remainscloses. Due to the brake application, vehicle speed decreases but doesnot decrease to a vehicle speed less than the threshold speed 507. Thus,sufficient motive air is provided to the aspirator system and thecooling fans are not activated.

At t2, the brake pedal is released and the vehicle resumes steady statetravel conditions, similar to those prior to t1, between t2 and t3. Thebrake booster vacuum remains above the minimum threshold vacuum 505 andthe vehicle speed remains above the threshold speed 507 and as a result,the check valve remains closed and the cooling fans remain deactivated.

At t3, the brake pedal may be applied again. Brake pedal application att3 may be more forceful (e.g., depressed further and faster) as comparedto the brake pedal application at t1. As a result, a steeper drop invacuum level within the brake booster vacuum is observed during thebrake application between t3 and t4. However, the brake booster vacuumremains above the minimum threshold vacuum 505. The vehicle speeddecreases due to the brake application and falls below the thresholdspeed 507 (e.g., a low speed or vehicle stop). Vehicle speeds below thethreshold speed 507 may not be able to provide the aspirator system witha sufficient motive flow for generating vacuum. However, the coolingfans remain in an off position because the check valve is not open. Inthis way, the brake booster does not desire vacuum and a sufficientmotive flow is not desired by the aspirator system.

At t4, the brake booster vacuum falls below the minimum threshold vacuum505. In response, the check valve moves to an open position. The brakesmay be released at t4. The vehicle speed remains below the thresholdspeed 507 resulting in an activation of the cooling fans to provide thedesired motive flow to the aspirator system to generate vacuum. Betweent4 and t5, an operator may depress an accelerator pedal resulting in thevehicle speed increasing. The cooling fans remain active for a totalduration of the vehicle speed being less than the threshold speed 507 incombination with the check valve being open. The generated vacuum fromthe aspirator system is applied to the brake booster until vacuum in thebrake booster is above the minimum threshold vacuum 505.

In one embodiment, additionally or alternatively, the brakes may not bereleased at t4 and vacuum may be consumed for braking applications. Asdescribed above, the check valve is opened as the brake booster vacuumfalls below the minimum threshold vacuum 505. Thus, the aspirator systemmay provide vacuum to the brake booster simultaneously to the brakebooster providing vacuum for braking applications.

At t5, the accelerator pedal remains depressed increasing the vehiclespeed beyond the threshold speed 507. The cooling fans are deactivatedin response to sufficient motive air being provided for generatingvacuum in the aspirator. Between t5 and t6, the brake booster vacuumlevel continues to increase but remains below the minimum thresholdvacuum 505. The check valve is open. Thus, the aspirator systemgenerates vacuum via motive flow produced from vehicular movement andprovides the vacuum to the brake booster.

At t6, the brake booster vacuum surpasses the minimum vacuum threshold505. The check valve closes in response to the brake booster vacuumincrease and the brake booster and aspirator system are no longer influid communication. After t6, the accelerator pedal may continue to bedepressed resulting in the vehicle speed increasing. The brake pedal maybe released. The check valve may be closed. The cooling fans may bedeactivated.

In this way, a brake booster vacuum may be replenished without flowingair from a vacuum reservoir to an intake manifold or other enginecomponent. An aspirator system generates vacuum with motive flow andprovides the vacuum to the brake booster when a check valve is open. Thecheck valve may be automatically opened when the vacuum of the brakebooster is less than a minimum threshold vacuum. One or more coolingfans may be located upstream of motive flow inlets of the aspiratorsystem to generate motive flow at low vehicle speeds and/or stops. Bydoing this, vacuum may be provided from the aspirator system to thebrake booster during a spectrum of vehicle conditions. The technicaleffect of using an aspirator system and brake booster system fluidlyseparated from an engine and its components is to eliminate usage of acontrol valve or other control system device for the replenishment ofvacuum to the brake booster.

An aspirator system for a vehicle includes a volute shaped aspiratorwith a linear aspirator protruding through a spiral of the voluteaspirator, the linear aspirator comprising a venturi passage fluidlycoupled to a brake booster, and where the aspirators are fluidly coupledto front or rear grills via a conical aspirator with no otherintervening components located therebetween. In a first example of theaspirator system, the conical aspirator is the furthest downstream andthe linear aspirator is the furthest upstream of the aspirators. In asecond example of the aspirator system optionally including the firstexample, further comprising a check valve located in a passage fluidlycoupling the brake booster to the venturi passage. A third example ofthe aspirator system optionally includes one or more of the first andsecond example, and further includes, the check valve opens in responseto a vacuum of the brake booster being less than a minimum thresholdvacuum. A fourth example of the aspirator system optionally includes oneor more of the first through third examples, and further includes, thevolute shaped aspirator and the linear aspirator further comprise inletsfor receiving motive air flow from the front grill. A fifth example ofthe aspirator system optionally includes one or more of the firstthrough fourth examples, and further includes, the inlets are locateddownstream of fans. A sixth example of the aspirator system optionallyincludes one or more of the first through fifth example, and furtherincludes, the aspirators generate vacuum during vehicle speeds greaterthan a threshold speed.

A method for an aspirator system includes generating vacuum via motiveflow in an aspirator system when a vehicle speed is greater than athreshold speed or when at least one cooling fan is activated, providingvacuum from the aspirator system to a brake booster in response to acheck valve being open, and mixing suck flow from the brake booster withmotive flow in the aspirator system and flowing the mixture directly outa rear grill without flowing the mixture through any other components. Afirst example of the method includes where activating the cooling fan isin response to the vehicle speed being less than the threshold speed. Asecond example of the method optionally including the first examplefurther includes the check valve being closed when a brake boostervacuum is greater than a minimum threshold vacuum. A third example ofthe method optionally including the first and/or second examples furtherincludes where generating vacuum includes flowing motive flow through aventuri passage, a spiral shaped passage, and an annular passage of theaspirator system. A fourth example of the method optionally includingthe first through third examples further includes activating the coolingfan is in response to a coolant temperature being greater than athreshold temperature. A fifth example of the method optionallyincluding the first through fourth examples further includes activatingthe cooling fan in response a combination of a vehicle speed being lessthan the threshold speed and the coolant temperature being less than thethreshold temperature further includes one or more or retarding spark,disabling coolant flow, and advancing spark timing.

An aspirator system of a vehicle comprising an engine with one or morecooling fans, an aspirator system with at least one inlet downstream ofand in fluid communication with the one or more cooling fans, a first,second, and third aspirator portions of the aspirator system fluidlycoupled and capable of receiving motive flow from a front grill andexpelling the motive flow out through a rear grill and a brake boostercomprising a passage with a check valve fluidly coupled with the firstaspirator portions with no other intervening components locatedtherebetween. A first example of the system includes where the firstaspirator portion is a venturi passage. A second example of the systemoptionally including the first example and further includes where thesecond aspirator portion is a volute shape, and where the firstaspirator portion extends through a spiral of the second aspiratorportion. A third example of the system optionally including the firstand/or second examples and further includes where the third aspiratorportion is a cone shape with an outlet located between outer and innerwalls of the third portion, where the outlet is an annular shape, andwhere a space between the outer and inner walls decreases toward therear grill. A fourth example of the system optionally includes one ormore of the first through third examples and further includes where aconnecting passage fluidly coupling the first and second aspiratorportions to the third portion. A fifth example of the system optionallyincludes the first through fourth examples and further includes wherethe first aspirator portion receives suck flow from the brake boosterwhen the check valve is open and flows a mixture of the suck flow andthe motive flow toward the rear grill. A sixth example of the aspiratorsystem optionally includes one or more of the first through fifthexamples and further includes where the first aspirator portion outletflow is linearly shaped and the second and third aspirator portionoutlet flows are annularly shaped. A seventh example of the aspiratorsystem optionally includes one or more of the first through sixthexamples and further includes where the check valve is spring loadedwith a predetermined tension based on a minimum threshold vacuum. Aneighth example of the system optionally includes one or more of thefirst through seventh examples and further includes where the checkvalve is not electrically actuated.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. An aspirator system, comprising: a volute shaped aspirator with alinear aspirator protruding through a spiral of the volute aspirator,the linear aspirator comprising a venturi passage fluidly coupled to abrake booster, and where the aspirators are fluidly coupled to front orrear grills via a conical aspirator with no other intervening componentslocated therebetween.
 2. The aspirator system of claim 1, wherein theconical aspirator is the furthest downstream and the linear aspirator isthe furthest upstream of the aspirators.
 3. The aspirator system ofclaim 1, further comprising a check valve located in a passage fluidlycoupling the brake booster to the venturi passage.
 4. The aspiratorsystem of claim 3, wherein the check valve opens in response to a vacuumof the brake booster being less than a minimum threshold vacuum.
 5. Theaspirator system of claim 1, wherein the volute shaped aspirator and thelinear aspirator further comprise inlets for receiving motive air flowfrom the front grill.
 6. The aspirator system of claim 5, wherein theinlets are located downstream of fans.
 7. The aspirator system of claim1, wherein the aspirators generate vacuum during vehicle speeds greaterthan a threshold speed.
 8. A method comprising: generating vacuum viamotive flow in an aspirator system when a vehicle speed is greater thana threshold speed or when at least one cooling fan is activated;providing vacuum from the aspirator system to a brake booster inresponse to a check valve being open; and mixing suck flow from thebrake booster with motive flow in the aspirator system and flowing themixture directly out a rear grill without flowing the mixture throughany other components.
 9. The method of claim 8, wherein activating thecooling fan is in response to the vehicle speed being less than thethreshold speed or a coolant temperature being greater than a thresholdtemperature.
 10. The method of claim 9, wherein activating the coolingfan in response a combination of a vehicle speed being less than thethreshold speed and the coolant temperature being less than thethreshold temperature further includes one or more or retarding spark,disabling coolant flow, and advancing spark timing.
 11. The method ofclaim 8, wherein generating vacuum includes flowing motive flow througha venturi passage, a spiral shaped passage, and an annular passage ofthe aspirator system.
 12. A system comprising, an engine with one ormore cooling fans; an aspirator system with at least one inletdownstream of and in fluid communication with the one or more coolingfans; a first, second, and third aspirator portions of the aspiratorsystem fluidly coupled and capable of receiving motive flow from a frontgrill and expelling the motive flow out through a rear grill; and abrake booster comprising a passage with a check valve fluidly coupledwith the first aspirator portions with no other intervening componentslocated therebetween.
 13. The system of claim 12, wherein the firstaspirator portion is a venturi passage.
 14. The system of claim 12,wherein the second aspirator portion is a volute shape, and where thefirst aspirator portion extends through a spiral of the second aspiratorportion.
 15. The system of claim 12, wherein the third aspirator portionis a cone shape with an outlet located between outer and inner walls ofthe third portion, where the outlet is an annular shape, and where aspace between the outer and inner walls decreases toward the rear grill.16. The system of claim 12, further comprising a connecting passagefluidly coupling the first and second aspirator portions to the thirdportion.
 17. The system of claim 12, wherein the first aspirator portionreceives suck flow from the brake booster when the check valve is openand flows a mixture of the suck flow and the motive flow toward the reargrill.
 18. The system of claim 12, wherein the first aspirator portionoutlet flow is linearly shaped and the second and third aspiratorportion outlet flows are annularly shaped.
 19. The system of claim 12,wherein the check valve is spring loaded with a predetermined tensionbased on a minimum threshold vacuum.
 20. The system of claim 12, whereinthe check valve is not electrically actuated.